IMMUNE HAEMOLYTIC ANAEMIAS

Dr Brian Mitchelson

IMMUNE HAEMOLYTIC ANAEMIAGeneral Principles

All require antigen-antibody reactions

Types of reactions dependent on:– Availability of complement

– Environmental Temperature

– Functional status of reticuloendothelial system

Manifestations– Intravascular haemolysis

– Extravascular haemolysis

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IMMUNE HAEMOLYTIC ANAEMIAGeneral Principles - 2

Antibodies combine with RBC, and either:

1. Activate complement cascade, &/or

2. Opsonize RBC for immune system

If 1: if all of complement cascade is fixed to red cell, intravascular cell lysis occurs

If 2: &/or if complement is only partially fixed, macrophages recognize Fc receptor of Ig &/or C3b of complement & phagocytize RBC, causing extravascular RBC destruction

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IMMUNE HAEMOLYTIC ANAEMIACoombs Test - Direct

Looks for immunoglobulin &/or complement of

surface of red blood cell (normally neither found

on RBC surface)

Coombs reagent - combination of anti-human

immunoglobulin & anti-human complement

Mixed with patient’s red cells; if immunoglobulin or

complement are on surface, Coombs reagent will

link cells together and cause agglutination of

RBCs

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IMMUNE HAEMOLYTIC ANAEMIACoombs Test - Indirect

Looks for anti-red blood cell antibodies in the patient’s serum, using a panel of red cells with known surface antigens

Combine patient’s serum with cells from a panel of RBC’s with known antigens

Add Coombs’ reagent to this mixture

If anti-RBC antigens are in serum, agglutination occurs

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HAEMOLYTIC ANAEMIA - IMMUNE

Autoimmune Haemolysis -2 types:

– Warm autoimmune haemolysis

– Cold autoimmune haemolysis

Alloimmune Haemolysis

– Haemolytic Transfusion Reaction

– Haemolytic Disease of the Newborn

Drug-Related Haemolysis

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Autoimmune Haemolytic Anaemia

(AHA)

Autoimmune haemolytic anaemia (AHA)

is characterized by shortened red blood

cell (RBC) survival and the presence of

autoantibodies directed against

autologous RBCs.

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AUTOIMMUNE HAEMOLYSIS

Due to formation of autoantibodies that

attack patient’s own RBC’s

Type characterized by ability of

autoantibodies to fix complement & site of

RBC destruction

Often associated with either

lymphoproliferative disease or collagen

vascular disease

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Autoimmune Haemolytic Anaemia

Classified by thermal reactivity – Warm reacts near 37 o C, Cold at 0-4 o C

Serologic evidence is positive DAT (direct Coomb’s test) with IgG or C3d present

Indirect Coomb’s test and specificity (serum / eluate)

Diagnostic Criteria-– serologic evidence and laboratory or clinical haemolysis

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AIHA Classification

Warm autoimmune haemolytic anaemia– Idiopathic, Secondary

• (Lymphoproliferative disorders, autoimmune diseases)

Cold autoimmune haemolytic anaemia– Cold agglutinin syndrome

• (Idiopathic, Secondary- mycoplasma, infectious mono, LPD)

– Paroxysmal cold haemoglobinuria• (Idiopathic, Secondary- measles, mumps, syphilis)

Drug-induced IHA – (Autoimmune, Drug adsorption, Neoantigen)

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AUTOIMMUNE HAEMOLYSISWarm Type

Usually IgG antibodies

Fix complement only to level of C3,if at all

Immunoglobulin binding occurs at all temps

Fc receptors/C3b recognized by macrophages

Haemolysis primarily extravascular

70% associated with other illnesses

Responsive to steroids/splenectomy

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Diagnosis

Anaemia.

Spherocytes in peripheral blood film.

Reticulocytes are increased.

Neutrophilia common.

RBC coated with IgG, complement or both

(detect using DAT).

Autoantibody —often pan-reacting but specificity

in 10–15% (Rh: mainly anti-e, anti-D or anti-c).

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Diagnosis

LDH increased.

Serum haptoglobin decreased.

Exclude underlying lymphoma (BM, blood

and marrow cell markers).

Autoimmune profile—to exclude SLE or

other connective tissue disorder.

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AUTOIMMUNE HAEMOLYSISCold Type

Most commonly IgM mediated

Antibodies bind best at 30º or lower

Fix entire complement cascade

Leads to formation of membrane attack complex, which leads to RBC lysis in vasculature

90% associated with other illnesses

Poorly responsive to steroids, splenectomy

Responsive to plasmapheresis

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Diagnosis

Anaemia.

Reticulocytes are increased.

Neutrophilia common.

Positive DAT—C3 only.

± Autoantibodies —IgG or IgM

– Monoclonal in NHL.

– Polyclonal in infection-related CHAD.

IgM antibodies react best at 4°C (thermal amplitude 4–

32°C).

Specificity

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Diagnosis

Anti-I (Mycoplasma).

Anti-i (infectious mononucleosis)—causes little

haemolysis in adults

Since RBCs have little anti-i (cf. newborn i >> I).

LDH increased.

Serum haptoglobin decreased.

Exclude underlying lymphoma (BM, blood and marrow

cell markers).

Autoimmune profile to exclude SLE or other connective

tissue disorder.

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IMMUNE HAEMOLYSISDrug-Related

Immune Complex Mechanism

– Quinidine, Quinine, Isoniazid

“Haptenic” Immune Mechanism

– Penicillins, Cephalosporins

True Autoimmune Mechanism

– Methyldopa, L-DOPA, Procaineamide,

Ibuprofen

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DRUG-INDUCED HAEMOLYSISImmune Complex Mechanism

Drug & antibody bind in the plasma

Immune complexes either– Sit on red blood cell

Antigen-antibody complex recognized by RE system

Red cells lysed as “innocent bystander” of destruction of immune complex

REQUIRES DRUG IN SYSTEM

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DRUG-INDUCED HAEMOLYSISHaptenic Mechanism

Drug binds to & reacts with red cell

surface proteins

Antibodies recognize altered protein, ±drug, as foreign

Antibodies bind to altered protein & initiate

process leading to hemolysis

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DRUG-INDUCED HAEMOLYSISTrue Autoantibody Formation

Certain drugs appear to cause antibodies

that react with antigens normally found on

RBC surface, and do so even in the

absence of the drug

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Drug-Induced Autoimmune

Haemolytic Anaemia

Prototype Drugs Clinical Findings Detection of

Drug-Induced

Antibody

Proposed

Mechanism

Stibophen Acute

Intravascular

Haemolysis

Serum +

Drug + Red Cells

Neoantigen

Penicillins/

Cephalosporin

Subacute

Extravascular

Haemolysis

Serum + Drug-

Coated Red Cells

Drug Adsorption

α-methyldopa Warm antibody

autoimmune

haemolytic

anaemia

Serum + Normal

Red Cells

Autoimmune

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Drug-Induced Positive Antiglobulin Tests

Mechanism DAT Serum and Eluate

Neoantigen

-Drug +RBC complex

C3 (sometimes IgG also) Serum reacts with rbcs

only in the presence of

drug; eluate non-reactive

Drug Adsorption (DA)

-Drug binds to RBC

IgG (sometimes C3 also) React with drug-coated

RBCs but not untreated

RBCs- Ab to drug

Autoantibodies

-WAIHA

IgG (rarely C3 also)

11-36% of pts

React with normal RBCs in

absence of drug

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Treatment - AIHA

WAIHA CAD PCH Drug-IHA

Folate

Corticosteroids

20% complete

response

Folate

Avoid cold

Treat secondary cause

Folate

Avoid cold

Treat if haemolysis

present

Splenectomy

60-75% response rate

Chlorambucil

Cytoxan,

α-Interferon

Treat infection Folate

Stop drugs

Cytotoxic drugs-

Cytoxan, Rituxan

Plasmapheresis ? Plasmapheresis Corticosteroids-severe

cases

Transfuse –least

incompatible

Transfuse-I+, blood

warmer

Transfuse- P+, blood

warmer

Transfuse

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ALLOIMUNE HAEMOLYSISHaemolytic Transfusion Reaction

Caused by recognition of foreign antigens on transfused blood cells

Several types– Immediate Intravascular Haemolysis (Minutes) - Due to

preformed antibodies; life-threatening

– Slow extravascular haemolysis (Days) - Usually due to repeat exposure to a foreign antigen to which there was a previous exposure; usually only mild symptoms

– Delayed sensitization - (Weeks) - Usually due to 1st exposure to foreign antigen; asymptomatic

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ALLOIMMUNE HAEMOLYSISTesting Pre-transfusion

ABO & Rh Type of both donor & recipient

Antibody Screen of Donor & Recipient,

including indirect Coombs

Major cross-match by same procedure

(recipient serum & donor red cells)

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Manifestations of Delayed

Haemolytic Transfusion ReactionsClinical

– Fevers

– Chills

– Symptoms of anaemia

– Jaundice

– Oliguria or anuria (uncommon)

– Generalized Bleeding (Rare)

Laboratory

– Unexplained anaemia (or decrease in haemoglobin)

– Positive direct antiglobulin test

– Haemoglobinemia

– Haemoglobinuria (Uncommon)

– Haemosiderinuria

– Decreased haptoglobin

– Responsible antibody in post-transfusion RBC eluate

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ALLOIMMUNE HAEMOLYSISHaemolytic Disease of the Newborn

Due to incompatibility between mother negative

for an antigen & foetus/father positive for that

antigen.

Rh incompatibility, ABO incompatibility most

common causes

Usually occurs with 2nd or later pregnancies

Requires maternal IgG antibodies vs. RBC

antigens in foetus

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HYDROPS FETALIS

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ALLOIMMUNE HAEMOLYSISHaemolytic Disease of the Newborn - #2

Can cause severe anaemia in foetus, with

erythroblastosis and heart failure

Hyperbilirubinaemia can lead to severe brain

damage (kernicterus) if not promptly treated

HDN due to Rh incompatibility can be almost

totally prevented by administration of anti-Rh D

to Rh negative mothers after each pregnancy

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The EndThank you for your attention.

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